A low anion gap results from an imbalance in the body’s pH levels. Healthcare professionals identify this “gap” by examining the results of a blood test that measures electrolyte levels.
To maintain health and function, the body needs a pH balance. This refers to the blood’s balanced levels of acids and alkali, or bases. Electrolytes are substances in the blood that carry an electrical charge and help maintain the body’s pH balance, and are vital to many other functions.
A person with a pH imbalance may have high acid levels, called “acidosis,” or high bases, known as “alkalosis.” A pH imbalance is a serious concern and indicates an underlying health condition.
Below, we explore the causes, symptoms, and treatments for a low — or a high—anion gap reading.
Normal anion gap readings range from 4 to 12 millimoles per litre (mmol/L). Readings outside this range may indicate a pH imbalance, which can stem from various health issues.
Having an anion gap reading in the low range is very rare, and it may stem from a laboratory error. A doctor usually orders a second test if an electrolyte blood test shows a low anion gap.
Hypoalbuminemia
A condition called hypoalbuminemia can cause a low anion gap reading. Hypoalbuminemia involves having too little of an essential protein called albumin in the blood. It typically occurs because of inflammation throughout the body.
Specific causes of hypoalbuminemia include:
- sepsis
- recent surgery
- malnutrition
- severe burns
- liver or kidney disease
- hyperkalemia, which is high potassium
- hypercalcemia, which is high calcium
- hypermagnesemia, which is high magnesium
- lithium toxicity
- cancer
When a person has too much acid or too little alkali in their blood, the anion gap reading will be higher than normal. This is called “high anion gap metabolic acidosis,” and it can be life threatening in some situations.
This type of acidosis may result from:
- uncontrolled diabetes
- kidney damage or failure
- certain medications, including metformin
- lactic acidosis, which is a buildup of lactic acid
- excessive alcohol use that causes alcoholic ketoacidosis
- exposure to high levels of aspirin, methanol, or antifreeze, among other chemical substances
- a drug overdose
- prolonged starvation
The symptoms of a pH imbalance depend on the cause.
Symptoms of alkalosis
It is rare for a person’s blood to be less acidic than average However, potential symptoms include:
- low calcium levels
- a headache
- lethargy
- weakness
- seizures, muscle spasms, and delirium
- heart palpitations
People may also experience symptoms consistent with the underlying condition affecting blood pH. For example, a person with alkalosis due to hypoalbuminemia may experience:
- fluid retention
- rapid heartbeat
- diarrhea, vomiting and nausea
- appetite changes
- hair thinning
- dry or itchy skin
Symptoms of acidosis
A person with acidosis, and thus a high anion gap reading, may have no symptoms or have symptoms related to the underlying health issue. These symptoms may include:
- nausea, with or without vomiting
- fatigue
- a headache
- drowsiness
- shortness of breath
- a rapid heart rate
- low blood pressure
Treatments can address the health issue responsible for an abnormal anion gap reading.
Measuring the anion gap alone cannot confirm any diagnosis, so a doctor performs a variety of other tests before making a diagnosis and a treatment plan.
Anyone concerned about a high or low anion gap reading should discuss the possible cause with their doctor.
Below are frequently asked questions relating to anion gap test results.
Should I be worried if my anion gap is low?
Low anion gap test results are often the result of mis-testing and are incredibly rare. However, they may indicate albumin deficiency. If further tests confirm a person has a low anion gap, medical assistance is essential.
What cancers cause low anion gaps?
Multiple myeloma, a type of bone marrow cancer, can cause a low anion gap. Certain cancer treatments may also impact potassium levels, leading to alkalosis.
How do I raise my anion gap?
Treating the underlying cause of an anion gap, either high or low, will help to stabilize blood pH levels.
A range of medical conditions can disrupt the balance of the body’s pH levels. Calculating the anion gap can help a doctor determine the cause of an imbalance.
A low anion gap reading is very rare, and it often results from a laboratory error. As a result, a doctor who finds a low reading typically orders a second test.
A high anion gap reading often signals a serious health problem, such as uncontrolled diabetes or a drug overdose. The person usually needs prompt treatment to prevent severe or fatal complications.
A doctor can provide more specific information about the likely cause of a low or high anion gap reading.